12 Refraction

Final Rx determination

The final Rx is the prescription that you propose handing to the patient at the end of your examination.  To determine this, consider all of the following factors:

• Refractive history, both distance and near
• Entering visual acuities, both distance and near
• Refraction
• Trial frame
• Potential adaptation issues.  With large changes, can you give less but still obtain the same benefit/VAs, i.e., minimum change for maximum benefit?
• Does it make sense mathematically, i..e., do you propose change a 1.5 D in an effort to gain one line of VAs.

Do not look at the numbers on the phoropter dials during retinoscopy (or subjective refraction)

If you’re glancing at the numbers, you’re not performing retinoscopy (or subjective refraction).  You’re typically trying to match what you’re getting with some pre-conceived goal.

Complete subjective refraction on one eye, then perform subjective refraction on the other eye

Complete all of the subjective refraction (visual acuities after retinoscopy, sphere check, cylinder axis and power) on the right eye before moving to the left eye.  You should not have to occlude each eye more than once.  Balance when finished.

Provide refractive choices slowly but steadily, with clear instructions to the patient

Repeat choices if the patient does not immediately respond, and cater your speed to the patient.

During step up, you ask, “Let me know when the line is blurry”

“Blurry” is a subjective experience.  Instead, consider directing the patient to let you know when they can no longer read any letters on the specified line – a more objective endpoint.

Trial Frame

It’s generally a good idea to perform a trial frame.  In trial framing, consider that you’ll typically compare the patient’s habitual Rx to your subjective Rx.  Therefore, consider using their glasses and the subjective in the phoroptor to perform this comparison, isolating the smallest line they can read for accurate comparison.

With small Rx changes, you perform a trial frame to determine if the patient perceives those changes.  Additionally, you have to consider the cost/benefit ratio of those changes with patient, specifically, “Is this change worth the cost of a new pair of glasses?”

After performing a trial frame, record the name of the test, the two things you compared (note that this may not always be Hx and Subjective), as well as the patient’s preference if their is one.  Record this in the notes section of the Subjective refraction line, as this is a subjective test.  As an example:

TF:  prefers hx v. subj.

If the patient has no distance or near complaints, and has 20/20 visual acuities in each eye, your refraction should take no more than…

2 minutes.  Your default setting in this situation is to prescribe the HxRx unless you have a REALLY GOOD REASON TO CHANGE IT; therefore, spend a few minutes attempting to refine the Rx, and then move on.

When you provide the patient a new eyeglass prescription, always educate them about adaptation

You can save yourself a lot of time (and therefore money) if you educate your patient about the need to adapt to their new prescription.

I usually use a variant of this script:  “Anytime you receive a new prescription, it may take a few weeks to get used to it.  If after two weeks of full-time wear you find that you’re having problems, please come back so that we can fix it for you.”  I recommend that you tell the patient this even if you provide them with a copy of their habitual Rx, as base curve changes between their new and old Rx may cause adaptation issues.

Also, make sure that you talk to the patient about bifocal adaptation, including stepping up or stepping down with care.